For example, Japanese Patent Application Publication No. H07-312852 discloses a permanent magnet type rotor, which is an integrated unit of a permanent magnet, a yolk part, and a shaft, formed by resin molding.
In the permanent magnet type rotor described above, there has been a risk of demagnetization when the integrated unit is formed by resin molding, due to the heat of the resin. In order to overcome such risk, disposing the permanent magnet between the yolk part after the yolk part (core piece part) is formed into an integrated unit by resin molding can be considered. When such method is employed, the permanent magnet is attached to either side of the neighboring yolk parts by using magnetic force.
However, it is difficult to intentionally attach a permanent magnet, which is disposed between the yolk part, to one side of the neighboring yolk part in a circumferential direction. For this reason, the location of the permanent magnet in the yolk part may vary per each permanent magnet, and the location of the permanent magnet in the circumferential direction may become irregular. Consequently, the magnetic flux generated by the permanent magnet becomes uneven, and further, the center of gravity balance in the circumferential direction of the permanent magnet type rotor becomes deteriorated. As a result, the rotation of the permanent magnet type rotor becomes unstable, and vibration and noise have been generated when the permanent magnet type rotor rotates.